Lower leg sensing device and method of providing data therefrom

ABSTRACT

A lower leg sensing device includes a housing, a leg attachment member and real time data providing member. The housing includes a position angle sensor, an magnetic field sensor, and a foot contact sensor. The leg attachment member is configured to facilitate attachment of the housing to the lower leg of a user. The real-time data providing member provides data, in real-time, pertaining to the angle of a lower leg of a user relative to a line of gravity upon contact with an outside surface by a leg of a user. A method of providing data to a user that is running or walking is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/859,196 filed on Apr. 9, 2013. The entire disclosure of theabove application is incorporated herein by reference.

FIELD

The invention relates in general to athletic training devices, and moreparticularly, to a lower leg angle sensing device which obtains datapertaining to a run or walk of a user, measuring, among other things,the angle of the lower leg when contacting the ground during activitiessuch as running (i.e., the shank angle, as defined below).

BACKGROUND

Recreational and competitive walking and running are activities enjoyedby millions. It is estimated that there are over 112 million fitnesswalkers in the United States alone, along with almost 40 millionrunners. There is a constant desire among these groups to increaseefficiency and performance while decreasing injury.

As a result, over the years, many advancements have appeared. Suchadvancements include advancements to equipment, namely, clothing andshoes. In the case of shoes, advancements have provided improvedcushioning, improved stability and improved gate, as well as an improvedlevel of comfort. Clothing has evolved high performance fabrics whichprovide sweat management techniques that enhance comfort and minimizeskin irritation.

Other advancements have come in the form of training aids. Suchadvancements include heart rate monitors and the like. Such advancementsassist by providing data pertaining to certain physical features (i.e.,heart rate). One interesting advancement has been in the form ofreal-time providing of data. For example, with current heart ratedevices, a user can be instantly advised as to current heart rate andcan be alerted as to changes in the heart rate. The user is then able tomake immediate changes and can watch to see what effect those changeshave on the parameter that is being tracked.

Even with these improvements, there remains a need to further improvethe efficiency and performance of walkers and runners, while reducingthe instances of injury as well as the severity of injuries.

Thus, it is an object of the present disclosure to provide additionaltraining aids to achieve improvements in efficiency and performancewhile reducing injury.

SUMMARY

The disclosure is directed to a method of providing data to a user thatis running or walking comprising the steps of: providing a lower legsensing device, the lower leg sensing device including at least aposition angle sensor and a foot contact sensor; coupling the lower legsensing device to a lower leg of a user; sampling the position anglesensor and the foot contact sensor; determining the angle of the lowerleg relative to a line of gravity based upon the data received from theposition angle sensor and the foot contact sensor; providing informationto a user pertaining to the angle of the lower leg relative to the lineof gravity.

In a preferred embodiment, the step of providing information to a usercomprises the steps of: comparing the angle that has been determined toa known range of acceptable angles; and providing a user understandablesignal to a user sufficient for the user to determine whether the anglethat has been determined is within the known range of acceptable angles.

In another preferred embodiment, the step of providing comprises thesteps of: providing a first user understandable signal if the angle thathas been determined is within the known range of acceptable angles;providing a second user understandable signal if the angle that has beendetermined is outside of the known range of acceptable angles on a firstside of the range; and providing a third user understandable signal ifthe angle that has been determined is outside of the known range ofacceptable angles on a second side of the range.

In another preferred embodiment, the first, second and third userunderstandable signals comprise at least one of audible, visual andkinesthetic signals.

In another preferred embodiment, the method further comprises the stepof: providing a computing device that is separated from the sensingdevice; establishing a communication link between the computing deviceand the sensing device; and transmitting data obtained through samplingof the position angle sensor and the foot contact sensor.

In another preferred embodiment, the method further comprises the stepof: displaying in real-time on the computing device the data obtainedthrough sampling of the position angle sensor and the foot contactsensor.

In yet another preferred embodiment, the computing device comprises asmartphone coupled wirelessly to the sensing device, and the step ofdisplaying comprises the step of displaying on a display of thesmartphone.

In some such embodiments, the smartphone further includes a GPS sensorand further includes a clock, the method further comprising the stepsof: computing at least one other parameter based upon the sensors,including, at least one of cadence, speed, time, stride length, andground contact time.

In another embodiment, the lower leg sensing device further includes: ahousing, wherein the position angle sensor and the foot contact sensorare positioned therewithin; and a leg attachment member configured toreleasably attach the housing to the lower leg of the user.

In another embodiment, the leg attachment member comprises a strap thatis configured to enable releasable attachment to the housing to an ankleregion of the lower leg of the user.

In another aspect of the disclosure, the disclosure is directed to alower leg sensing device comprising a housing and a leg attachmentmember and a real-time data providing means. The housing has a positionangle sensor and a foot contact sensor. The leg attachment member isconfigured to facilitate attachment of the housing to the lower leg of auser. The real-time data providing means provides data pertaining to theangle of a lower leg of a user relative to a line of gravity uponcontact with an outside surface by a leg of a user.

In a preferred embodiment, the providing means further comprises acomputing device and a signal member. The computing device is wirelesslycoupled to the position angle sensor and the foot contact sensor. Thesignal member is coupled to the computing device. The signal member iscapable of providing a user understandable signal.

In another preferred embodiment, the user understandable signal may beany one of audible, visual and kinesthetic signals. Such signals maylikewise include silence.

In another preferred embodiment, the computing device further comprisesa smartphone wherein the signal member comprises at least one of thedisplay of the smartphone, a speaker of the smartphone and a vibrationmechanism of a smartphone.

DRAWINGS

The disclosure will now be described with reference to the drawingswherein:

FIG. 1 of the drawings is a schematic representation of the device ofthe present disclosure, showing, in particular, communication thereofwith an outside device;

FIG. 2 of the drawings is a partial perspective view of the devicecoupled to a leg of a user;

FIG. 3 of the drawings is a schematic composite view of the device ofthe present disclosure, showing, in particular, the incorporation of thehousing within the leg attachment member;

FIG. 4 of the drawings is a plurality of screenshots from a computingdevice electronically coupled to the device, showing, in particular, thecalibration of the device for a particular user;

FIG. 5 of the drawings is a plurality of screenshots from a computingdevice electronically coupled to the device, showing, in particular,real-time feedback of various parameters and data pertaining to acurrent use by a user, such information including the distance traveled,the time utilized, leg angle, cadence, pace, and an overall “smartscore” which corresponds to an algorithm that provides a grade for thecurrent activity;

FIG. 6 of the drawings is a plurality of screenshots from a computingdevice electronically coupled to the device, showing, in particular,summaries of past exercise routines as well as information pertaining toeach, including the overall “smart score” that has been determinedthrough analysis of all of the prior activities (or a predeterminedportion of the same). Additionally, options to export the results tosocial media and to otherwise share (i.e., through email) are provided;

FIG. 7 of the drawings is a schematic representation of a computingdevice of the present disclosure;

FIG. 8 a schematic of the system according to the present teachingshaving magnetometer and accelerometer;

FIG. 9 depicts the fixed magnet usable in the system according to thepresent teachings;

FIG. 10 represents a measures magnetic flux density at x,y separationfrom the detector according to the present teachings;

FIG. 11 represents a generic runner's stride as measured by the presentsystem;

FIG. 12 represents the stride of an elite male sprinter;

FIG. 13 represents the stride of a first user having a rearfoot strike;

FIG. 14 represents the stride of a second user having a rearfoot strike;

FIG. 15 represents the stride of a third user having a rearfoot strike;

FIG. 16 represents force vs. time data for the stride of a user having aforefoot strike;

FIG. 17 represents force vs. time data for the stride of a user having aforefoot strike;

FIG. 18 represents displacement vs. impact data for the stride of a userhaving a forefoot strike;

FIG. 19 represents displacement vs. impact data for the stride of a userhaving a forefoot strike;

FIG. 20 represents displacement vs. impact data for the stride of a userhaving a rearfoot strike;

FIG. 21 represents the comparison for vs. impact data for the stride ofa user having a rearfoot and forefoot strike;

DETAILED DESCRIPTION OF THE DISCLOSURE

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and described herein in detail aspecific embodiment with the understanding that the present disclosureis to be considered as an exemplification and is not intended to belimited to the embodiment illustrated.

It will be understood that like or analogous elements and/or components,referred to herein, may be identified throughout the drawings by likereference characters. In addition, it will be understood that thedrawings are merely schematic representations of the invention, and someof the components may have been distorted from actual scale for purposesof pictorial clarity.

Referring now to the drawings and in particular to FIG. 1, the lower legsensing device is shown generally at 10. The sensing device isconfigured to interface with an outside computing device, such assmartphone 101. It will be understood that the outside computing devicemay comprise any one or more of a general purpose computer, tabletcomputer, smartphone, PDA, smart watch, special purpose computingdevice, among others. Thus, while in the disclosure below, referencewill be made to smartphone 101, with the understanding that a number ofother devices are likewise contemplated for use. Details pertaining tothe computing device are described in the following paragraphs.

It will be understood that although not required, aspects of thedescriptions below will be provided in the general context ofcomputer-executable instructions, such as program modules, beingexecuted by a computing device, sensing device alone or in cooperationwith other remote computing devices through outside communication (whichwill also be described).

More specifically, aspects of the description below will reference acts,methods and symbolic representations of operations that are performed byone or more computing devices or peripherals, unless indicatedotherwise. As such, it will be understood that such acts and operations,which are at times referred to as being computer-executed, include themanipulation by a processing unit of electrical signals representingdata in a structured form. This manipulation transforms the data ormaintains it at locations in memory, which reconfigures or otherwisealters the operation of the computing device or peripherals in a mannerwell understood by those skilled in the art. The data structures wheredata is maintained are physical locations that have particularproperties defined by the format of the data.

Generally, program modules include routines, programs, objects,components, data structures, and the like that perform particular tasksor implement particular abstract data types. Moreover, those skilled inthe art will appreciate that the computing devices need not be limitedto a specialized control module within the housing of the device, orconventional personal computers, and include other computingconfigurations, including hand-held devices (i.e., smartphones),multi-processor systems, microprocessor based or programmable consumerelectronics, network PCs, minicomputers, mainframe computers, and thelike. Similarly, the computing devices need not be limited to astand-alone computing device, as the mechanisms may also be practiced indistributed computing environments linked through a communicationsnetwork. In a distributed computing environment, program modules may belocated in both local and remote memory storage devices.

With reference to FIG. 7, an exemplary general-purpose computing deviceis illustrated in the form of the exemplary general-purpose computingdevice 100. The general-purpose computing device 100 may be of the typeutilized for the device 10 or for the outside computing devices 101(FIG. 1) as well as the other computing devices which may comprise theoutside computing device servers with which communication can beestablished. As such, it will be described with the understanding thatvariations can be made thereto. The exemplary general-purpose computingdevice 100 can include, but is not limited to, one or more centralprocessing units (CPUs) 120, a system memory 130 and a system bus 121that couples various system components including the system memory tothe processing unit 120. The system bus 121 may be any of several typesof bus structures including a memory bus or memory controller, aperipheral bus, and a local bus using any of a variety of busarchitectures. Depending on the specific physical implementation, one ormore of the CPUs 120, the system memory 130 and other components of thegeneral-purpose computing device 100 can be physically co-located, suchas on a single chip. In such a case, some or all of the system bus 121can be nothing more than communicational pathways within a single chipstructure and its illustration in FIG. 3 can be nothing more thannotational convenience for the purpose of illustration.

The general-purpose computing device 100 also typically includescomputer readable media, which can include any available media that canbe accessed by computing device 100. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes mediaimplemented in any method or technology for storage of information suchas computer readable instructions, data structures, program modules orother data. Computer storage media includes, but is not limited to, RAM,ROM, EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can be accessed by the general-purpose computing device 100.Communication media typically embodies computer readable instructions,data structures, program modules or other data in a modulated datasignal such as a carrier wave or other transport mechanism and includesany information delivery media. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared, Bluetooth and other wireless media. Combinations of the any ofthe above should also be included within the scope of computer readablemedia.

When using communication media, the general-purpose computing device 100may operate in a networked environment via logical connections to one ormore remote computers. The logical connection depicted in FIG. 1 is ageneral network connection 171 to the network 190, which can be a localarea network (LAN), a wide area network (WAN) such as the Internet, orother networks. The computing device 100 is connected to the generalnetwork connection 171 through a network interface or adapter 170 thatis, in turn, connected to the system bus 121. In a networkedenvironment, program modules depicted relative to the general-purposecomputing device 100, or portions or peripherals thereof, may be storedin the memory of one or more other computing devices that arecommunicatively coupled to the general-purpose computing device 100through the general network connection 171. It will be appreciated thatthe network connections shown are exemplary and other means ofestablishing a communications link between computing devices may beused.

The general-purpose computing device 100 may also include otherremovable/non-removable, volatile/nonvolatile computer storage media. Byway of example only, FIG. 1 illustrates a hard disk drive 141 that readsfrom or writes to non-removable, nonvolatile media. Otherremovable/non-removable, volatile/nonvolatile computer storage mediathat can be used with the exemplary computing device include, but arenot limited to, magnetic tape cassettes, flash memory cards, digitalversatile disks, digital video tape, solid state RAM, solid state ROM,and the like. The hard disk drive 141 is typically connected to thesystem bus 121 through a non-removable memory interface such asinterface 140.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 3, provide storage of computer readableinstructions, data structures, program modules and other data for thegeneral-purpose computing device 100. In FIG. 1, for example, hard diskdrive 141 is illustrated as storing operating system 144, other programmodules 145, and program data 146. Note that these components can eitherbe the same as or different from operating system 134, other programmodules 135 and program data 136. Operating system 144, other programmodules 145 and program data 146 are given different numbers here toillustrate that, at a minimum, they are different copies.

Referring again to FIG. 1, the lower leg sensing device 10 is configuredto, primarily, sense the location of the foot relative to the pavement,and, simultaneously, the lower leg angle (commonly referred to as theshank angle). More particularly, the lower leg angle is the angle of thelower leg relative to vertical at the moment of ground contact (withvertical being the direction of the force vector of gravity extendingthrough the center of the knee). The angle is generally defined by amid-coronal line extending from the center of the knee joint (lateralside) through the central of the lateral malleolus). Thus, it will beunderstood that vertical corresponds to a line extending through thecenter of the knee joint (lateral side) and in the direction of theforce vector of gravity (commonly referred to as the line of gravity).Additionally, reference to lower leg angle, herein, refers to the shankangle as defined. Advantageously, with such information, angularvelocity of the lower leg, ground contact time of the foot, runningspeed, step cadence, ground impact transient and lower leg position canbe tracked. Furthermore, information can be provided to the user to aidthe user in making adjustments to his/her running gate. Such improvementleads to improved form, and speed, with a reduction in injurypropensity.

With reference to FIG. 2, the lower leg sensing device 10 includeshousing 12 and leg attachment member 14. The housing 12 includes acavity within which a computing device 23, including some of thecomponents identified above (such as an outside communication portion27, can be positioned. To the computing device, a plurality of sensorscan be coupled. The plurality of sensors include a position angle sensor20 and a foot contact sensor 22. The housing 12 may comprise a pluralityof components which are coupled together to form the cavity.Additionally, the housing can have an accommodation for a power source25, such as a rechargeable battery, a disposable battery or the like.

As to the sensors, the position angle sensor 20 comprises a sensor thatcan determine an angular position relative to a known angular position,or a sensor that can sense a change in angular position. Such sensorsare known to those of skill in the art. The foot contact sensorcomprises an accelerometer. Such a sensor is likewise known in the art.Such a sensor can sense the change in acceleration (and in turn positionor velocity). An on/off switch, as well as an audible signal generator(speaker, piezoelectric element) can also be included (or a visualsignal, such as an LED, or a kinesthetic signal, such as a vibratingelement).

The leg attachment member 14 is shown as comprising band 30. The band 30includes a first end 31 and a second end 32, an inner surface 36 and anouter surface 38. An attachment member couples the first end to thesecond end to make a hoop that can be installed to extend about the legof a user. In an embodiment, the hook and loop portion may be on thefirst end, with a ring at the second end. The first end is insertedthrough the ring at the second end and then folded over itself so as tocouple the hook and loop portions together. In the embodiment shown, theattachment member comprises a hook and loop fastener, wherein a firstcomponent is coupled to the first end and a second component is coupledto the second end. In the embodiment shown, the housing can be insertedinto a pocket 41 that is created within the band 30. In such anembodiment, a slit may be disposed on the inner surface 36, and mayprovide access to the pocket. In another embodiment, the housing iscoupled to the outside surface of the band 30. In other embodiments, theband 30 may be co-molded with a portion of the housing, so as to appearas a single integrally formed member.

In operation, the user first straps the sensing device 10 to his or herleg. The user insures that the power source (i.e., battery) is properlyinstalled and that there is power to the various components. Oncepositioned, the user can adjust position and retention of the band toinsure that the device remains stationary on the leg of the user.

Once fully installed, the position angle sensor can be calibrated. It iscontemplated that the position angle sensor is calibrated to set abaseline position. For example, the position angle sensor can becalibrated so that the initial resting position (wherein the lower legof the user is substantially vertical) is defined. To set a baselineposition, a button may be disposed on the device which may be pressed,after which the user can position the foot vertically for a period oftime (which time can be announced by the device through audible tones,vibrations or the like).

Once calibrated, the device can be activated so as to begin logging(which again can be achieved through a button disposed on the device).As the user runs, the two sensors can be sampled at a predeterminedrate. For example, each of the sensors can be sampled at 1000, 10,000,1000,000 Hz, 1 MHz, etc. Of course, this is exemplary only, and it iscontemplated that any number of sampling rates could be employed, withthe understanding that the slower the sampling rate, the lessdata/accuracy is achieved, whereas the faster the sampling rate, themore data that is obtained.

Among other data, the system can log data with respect to time. Thus, ateach sampling, the data pertaining to the position angle and the datapertaining to the foot contact sensor is read and stored. In such anembodiment, the data can be stored in volatile and/or nonvolatilememory. In some embodiments, a provision can be made for a removablestorage medium (i.e., a memory card, such as a microSD card, or thelike). When the user is done logging information, a button can bepressed to stop the recording of data.

It will be understood that the device may provide some level ofprocessing of the information that is received from the sensors. Forexample, as the user runs, the foot having the sensor proceeds up anddown with each running stride. When the foot of the user hits theground, further downward movement stops (i.e., the foot experiences ahigh rate of deceleration). Conversely, when the foot leaves the ground,the foot experiences an elevated rate of acceleration. Thus, it can bedetermined, based on the data from the foot contact sensor, when thefoot hits the ground and when the foot releases from the ground.

Thus, to determine the shank angle, a (FIG. 1) when contact with theground is achieved, it is necessary to obtain the angular position ofthe lower leg relative to the line of gravity when there is an abruptdeceleration of the foot sensed by the foot contact sensor.

It is known that the angular disposition of the lower leg when the footcontacts the ground should be close to matching the line of gravity.Such a position has been found to define the proper running form, assuch a position enhances efficiency and reduces injury. Thus, the dataobtained from these sensors can provide the precise angle of the lowerleg upon impact of the foot with the ground.

With additional processing, it is possible to provide real-time feedbackto the user relative to the shank angle. For example, if the lower legis within the proper range (i.e., vertical+/−5 degree), a first audiblesignal can be emitted. If the lower leg is too far from vertical (i.e.,the line of gravity) in either direction, a second audible signal can beemitted. Additionally, two different second audible signals can betransmitted, one if the lower leg is too far from vertical in onedirection, and a second if the lower leg is too far from vertical in theother direction. It will also be understood that the signal to the usermay be in a form other than audible. For example, such signals maycomprise audible, visual and kinesthetic signals. In other words, avisual feedback may be provided, such as a flashing light, or akinesthetic signal, such as a vibration. Additionally, it iscontemplated that combinations of signals may be utilized. It is alsocontemplated that the first audible signal (or other signal) can besilence or no signal at all. Such lack of any signal, it will beunderstood, corresponds to a condition wherein the activity isproceeding within all proper parameters.

This means for providing real-time data pertaining to the angle of alower leg of a user relative to the line of gravity upon contact with anoutside surface by a leg of a user provides information that the usercould not otherwise obtain—it is virtually impossible to determine theangle of the lower leg with any precision on someone else while running,much less on oneself when running Thus, real-time analysis has not beenpossible as to lower leg angle. Moreover, the user can attempt to makeadjustments, and receive feedback in a real-time manner as to theeffectiveness of these adjustments.

In other embodiments, and in most preferred embodiments, the device canbe configured to interface with a smartphone 101 on a real-time basis,wherein the features, calibrations, and settings are all set from anapplication within the smartphone 101. For example, the device can beconfigured to communicate with the smartphone 101 first. Any number ofdifferent protocols are contemplated, as identified above with respectto the computing device. Additionally, other short range protocols arelikewise contemplated, including by not limited to WIFI, zigbee,cellular, Bluetooth, RF and the like. One particular embodiment takesadvantage of the low power Bluetooth protocol found in Bluetooth 4.0specification. Of course, the device is not limited to any particulartype of communication protocol. It is also contemplated that a wiredsolution may be employed in certain embodiments, such as a USBcommunication protocol or the like.

In such embodiments, the data obtained through the sensors can betransmitted real-time to the smartphone. The smartphone includes aprogram that can calculate any number of different parameters from thedata received, and, optionally provide some sensors of its own (i.e.,GPS, clock, among others). Thus, the cell phone can initiate the audiblesignals contemplated above that correspond to the particular angle ofthe lower leg of the user. Additionally, the communication relative tocalibration, resetting, data purging, among others can all be controlledfrom the smartphone. The smartphone can also compile the data and storethe data.

It is contemplated that the data that is gathered can be transmitted toan outside server for further analysis. Such analysis may include theapplication of certain algorithms to the data to determine patterns, andto also prescribe certain training regimen. In addition, problematicconditions can be determined prior to such conditions becoming aproblem.

With reference to FIGS. 4 through 6, one embodiment of the use of thedevice in association with an outside computing device (in this case asmartphone) is shown. Specifically, when the smartphone application islaunched for the first time (or when users change), the user is promptedto provide profile information. This information my include name, age,height, gender, desired units for output, among others. Once entered,the system prompts the user to put the device on his or her ankle (ifthe same has not yet been done). The device is then turned on. Onceready, the user starts the calibration process by running for a minuteafter hitting the start (or begin) button on the smartphone. The initialcalibration provides the system with the general information as to theuser's particular parameters during running Once calibrated, the deviceis ready for use.

The user can then start to walk or run. The device will sample thedifferent sensors and provide the data, preferably wirelessly, to thesmartphone. The smartphone application then processes the data, alongwith, for example, data from its own sensors (i.e., GPS, clock etc.) toprovide output to the user. Among other data, the application canprovide information pertaining to form (steps per minute, lower legangle, time of foot contact), speed, and endurance. The information canbe provided real-time to the user. It is contemplated that theinformation as to the instant condition can be displayed on thesmartphone, and, if any of the parameters are outside of the desiredrange, an audible signal (or kinesthetic signal—vibration) can betriggered. The signals can be different and parameter dependent (as wellas condition dependent) so that the user has the information necessaryto understand not only which parameter, but the reason for the alert.The user can then take the appropriate action.

The system can, through a predetermined algorithm provide a score to theparticular run during or after completion, to provide the user with anoverall understanding of the quality of the run. Additionally, duringthe run, the system can audibly (or otherwise—vibration, lights, etc.)provide the user with information as to the current form or otherproblems that can be corrected by the user.

After a run is complete, the application can store the differentcompleted runs (or training sessions). The data pertaining to the runcan be transmitted to a remote computer (or server, or cloud storagesystem). Access can be provided to the data to, for example, a personaltrainer, coach, etc. That individual can analyze the data and providefeedback as to any number of different items. Furthermore, the user canshare the scores and the different runs on social media sites.

As previously described, the system can use an accelerometer to find theangle of the leg with respect to gravity. As shown in FIG. 8 amagnetometer and a fixed magnet can accurately determine the legcrossing point in the stride, which will harmonically discipline theaccelerometer. The magnetometer was determined to be the best of severaloptions, which included an ultrasound Doppler solution, inductivecoupling, and a RF amplitude proximity sensor.

The magnetometer has the benefit of being an inexpensive, simple, andlow power solution. The theory of operation is that a sensor will beattached to either ankle of the runner, facing inward. One sensor canhave a small magnet, and the other can have a 3-axis magnetometer. Bothsensors will include a 3-axis accelerometer, and can include a BlueTooth Low-Energy transceiver, memory for data logging and a USB port forcharging the battery and downloading collected data. The sensors performbasic data reduction and data logging; they are be able to communicatethe data to a third device using a Blue Tooth Low Energy (BLE) protocolor USB. The sensors are battery powered, and rechargeable through amicro-USB connector.

As described, the accelerometers are able to determine position using adouble integration, and small errors become cumulative over time. Inorder to overcome this problem, a means of nulling the drift in theaccelerometer is preferably included in a viable sensor system. Toaccomplish the nullification of the drift, a magnetometer is used toaccurately indicate the point at which one leg passes near the other.With this information, it is possible to operate the accelerometer as aharmonic measurement instrument and reconstruct the stride of therunner.

The system can be formed of several blocks: the magnet/magnetometer, theaccelerometer, the communication and data-logging control, and thebattery and battery charging circuitry. The data can be transmitted to anearby computer through a wireless communication or wire for datalogging. The product is understood to be a circuit that preferably: 1.provides an accelerometer measurement of sufficient accuracy and dynamicrange to measure the form of the stride; 2. Provides a method to zerothe drift in the accelerometer measurements; 3. Provides method togather and log the data, (transmit to an data gathering device); 4. Thecost of the sensor system is less than $40; 5. Powered for at least 4hours of operation; and 6. Mountable on the ankle of the user.

Using a magnetometer to correct and to zero the drift in theaccelerometers requires some analysis using a processor. The intensityand direction of the magnetic field about a permanent magnet, theselection of a magnet, how to detect the point in the stride where theankles are nearest, and the selection of a magnetometer.

At a sufficient distance from the source, a permanent magnet may beapproximated as a dipole. The magnetic flux density about the magneticmoment is given by: Where is the magnetic dipole moment, is thespherical radial coordinate, denotes the unit vector of the direction,and is the free space magnetic permeability. The strength of commercialpermanent magnet is specified in residual flux density, or residualinduction. The residual induction is specified according to the flux onthe axis of a cylindrical magnet: where is the length of the magnet, isthe radius of the cylinder, and is the coordinate of the axis of thecylinder. To convert residual flux density to magnetic dipole moment, weconsider the dominate functional component for.

At a sufficient distance from the source, a permanent magnet may beapproximated as a dipole. The magnetic flux density about the magneticmoment is given by:

${\overset{\_}{B}\left( \overset{\_}{r} \right)} = {\frac{m\;\mu_{0}}{4\;\pi\; r^{3}}\left( {{3{\hat{r}\left( {\hat{m} \cdot \hat{r}} \right)}} - \hat{m}} \right)}$Where m is the magnetic dipole moment, r is the spherical radialcoordinate, ^ denotes the unit vector of the direction, and mu₀ is thefree space magnetic permeability.

${B_{z}(z)} = {\frac{B_{r}}{2}\left( {\frac{L + z}{\sqrt{R^{2} + \left( {L + z} \right)^{2}}} - \frac{z}{\sqrt{R^{2} + z^{2}}}} \right)}$The strength the of commercial permanent magnet is specified in residualflux density, or residual induction. The residual induction is specifiedaccording to the flux on the axis of a cylindrical magnet:

where L is the length of the magnet, R is the radius of the cylinder,and Z is the coordinate of the axis of the cylinder. To convert residualflux density to magnetic dipole moment, we consider the dominatefunctional component for Z>>L,R.

FIG. 8 a schematic of the system according to the present teachingshaving magnetometer and accelerometer. Shown is a process couples toexternal memory and a power supply. Additionally coupled to theprocessor is a magnetometer and a tri-axial accelerometer.

FIG. 9 depicts the fixed magnet usable in the system according to thepresent teachings the magnets can have the following properties:

Different ceramic materials have different residual flux densities. Thecheapest magnets are made from Flux at distance hard ferrite ceramics.The strongest of 0.050″ magnets are made from neodinium- Residual Fluxfrom surface iron-boron Material and Grade Density, Br of magnet Ceramic1 2,200 629 Ceramic 5 3,950 1,130 SmCo 18 8,600 2,460 SmCo 26 10,5003,004 NdFeB 35 12,300 3,518 NdFeB 42H 13,300 3,804

In North America, the Earth's magnetic field is typically around 0.2 Gand does not exceed 0.3 G. This component can be removed through aprimitive spectral analysis that captures only the time-harmonicportions of the varying magnetic field. Typical magnetometers have adynamic range of ±8 G. As the intensity of the measured magnetic fieldis such a strong function of the distance from the magnet, determiningthe point at which the ankles are nearest is a well-conditioned problem.The magnitude of the magnetic flux density as a function of z-separationand x/y displacement is shown in FIG. 10. The coordinate system is shownin FIG. 9.

Optionally, the Honeywell HMC5883L magnetometer for this application. Itis a 3-axis, low-noise, 12-bit magnetometer with an ±8 G dynamic rangethat costs approximately $1.50 in quantity. The magnetometer iscompatible with a simple 2-wire I₂C interface. The accelerometer, can bethe Analog Devices ADXL345. It is a 3-axis accelerometer with 16-bitresolution and a ±16 g dynamic range. It is compatible with standard2-wire I₂C interfaces, is widely commercially available, and has minimaldevelopment risks.

Communication and processing can be accomplished using a TI CC2540F256Blue Tooth Low Energy modem with integrated 8051 microcontroller and256K flash memory. This single part will satisfy the requirements forboth a microprocessor and a modem. We recommend using a printedinverted-F matched to 2.4-2.5 GHz band through a Johansson 2450BLBluetooth Balun. Depending upon the final size constraints, the printedantenna may be altered for a less efficient, but smaller chip antenna.The CC2540 is USB compatible for communication.

The device be powered using a 3V rechargeable 100 mAh coin cell. Thebattery will be recharged using a Max8601 Li-Ion battery charger whichis designed to fully and safely charge lithium batteries from a USBpower source. Based upon preliminary estimates, a 100 mAh should provideat least 4 hours of operation.

FIG. 11 represents a generic runner's stride as measured by the presentsystem. Starting at a strides furthest extension 30. The segment betweenthe furthest extension 30 and the moment the foot makes contact with theground is defined as zone 1. Between the moment of ground contact andthe point the runner's shank angle is at “zero” shank angle is definedas zone two. As the foot is pulled back toward the runner. Zone three isdefined between the zero shank angle and the moment the toe leaves theground. Zone four is defined between the time or point the toe leavesthe ground to the point of furthest backward extension. The system isconfigured to reduce the size of zone two for all runner's strides.

FIG. 12 represents the stride of an elite male sprinter. Shown are notonly the points of zones one through zone four. As can be seen, the peakvertical force for an elite male sprinter is after zone two or when theshank angle passes through zero.

FIG. 13 represents the stride of a first user having a rearfoot strike.Shown are not only the points of zones one through zone four. As can beseen, the peak vertical force for an runner who has a rear foot strikeis within zone two or before the shank angle passes through zero. Asecond force peak was developed within the third zone.

FIG. 14 represents the stride of a second user having a rearfoot strike.Shown are not only the points of zones one through zone four. As can beseen, the peak vertical force for an runner who has a rear foot strikeis within zone two or before the shank angle passes through zero. Asecond force peak was developed within the third zone.

FIG. 15 represents the stride of a third user having a rearfoot strike.As shown in the Time vs Force graph, the heal strike stride presents ashock zone where the runner is breaking or slowing down, prior to theshank angle of zero. A second peak is reached within zone three afterthe shank angle is zero.

FIG. 16 represents force vs. time data for the stride of a sprinterhaving a forefoot strike. As can be seen, there is no deleterious shockzone which may be the cause of damage to runner's knees and ankles. FIG.17 represents force vs. time data for the stride of a user having aforefoot strike. As shown, the brake zone occurs but the deleteriousforce spike does not appear prior to the vertical shank angle. FIGS. 18,19, and 20 represent displacement vs. impact data for the stride of aElite male sprinter, a forefoot striking runner, and rearfoot strikingrunner. Shown are the first, second third, and fourth zone.

FIG. 21 represents the comparison force vs. impact data for the strideof a user having a rearfoot and forefoot strike. As shown, the solidline represents a heal strike runner having a high sharp impact load inzone one and prior to the zero shank angle. This is opposed to thedashed line where the fore foot engagement does not have the deleterioushigh impact load.

The foregoing description merely explains and illustrates the inventionand the invention is not limited thereto except insofar as the appendedclaims are so limited, as those skilled in the art who have thedisclosure before them will be able to make modifications withoutdeparting from the scope of the invention.

What is claimed is:
 1. A method of providing data to a user that isrunning or walking comprising the steps of: providing a lower legsensing device having a mounting member configured to mount the lowerleg sensing device on a user leg between the user's knee and ankle, thelower leg sensing device including at least a position angle sensorconfigured to measure a shank angle of the user at a time of a footcontact and a foot contact sensor and a magnetic field measurementsystem configured to measure a magnet positioned on a user leg; couplingthe lower leg sensing device to a lower leg of a user between the user'sknee and ankle; sampling the position angle sensor and the foot contactsensor; determining the angle of the lower leg relative to a line ofgravity based upon the data received from the position angle sensor andthe foot contact sensor; providing information to a user pertaining tothe angle of the lower leg relative to the line of gravity; comparingthe angle that has been determined to a known range of acceptable anglesusing a program module; providing a user understandable signal to a usersufficient for the user to determine whether the angle that has beendetermined is within the known range of acceptable angles; providing afirst user understandable signal if the angle that has been determinedis within the known range of acceptable angles; providing a second userunderstandable signal if the angle that has been determined is outsideof the known range of acceptable angles on a first side of the range. 2.The method of claim 1 wherein the first and second understandablesignals comprise at least one of audible, visual and kinestheticsignals.
 3. The method of claim 1 further comprising the steps of:providing a computing device that is separated from the sensing device;establishing a communication link between the computing device and thesensing device; and transmitting data obtained through sampling of theposition angle sensor and the foot contact sensor.
 4. The method ofclaim 3 further comprising the step of: displaying in real-time on thecomputing device the data obtained through sampling of the positionangle sensor and the foot contact sensor.
 5. The method of claim 3wherein the computing device comprises a communication device coupledwirelessly to the sensing device, and the step of displaying comprisesthe step of displaying on a display of the communication device.
 6. Themethod of claim 5 wherein the communication device further includes aGPS sensor and further includes a clock, the method further comprisingthe step of: computing at least one other parameter based upon thesensors, including, at least one of cadence, speed, time, stride length,and ground contact time.
 7. The method of claim 1 wherein the lower legsensing device further includes: a first housing, wherein the positionangle sensor and the foot contact sensor are positioned therewithin; anda leg attachment member configured to releasably attach the housing tothe lower leg of the user above the user's ankle.
 8. The method of claim7 wherein the lower leg sensing device further includes: a secondhousing, wherein the magnet is positioned therewithin.
 9. A lower legsensing device for measuring a lower angle between a user's knee andankle, the lower leg sensing device comprising: a position angle sensor,a magnetic field sensor and a foot contact sensor; a leg attachmentmember configured to facilitate attachment of the position angle sensorand a foot contact sensor to the lower leg of a user above the user'sankle; and a module configured to provide real-time data pertaining tothe angle of a lower leg of a user relative to a line of gravity impactof a foot with a ground surface by the user, said module further beingconfigured to comparing the angle that has been determined to a knownrange of acceptable angles using a program module and provide a userunderstandable signal to a user sufficient for the user to determinewhether the angle that has been determined is within the known range ofacceptable angles and compare changes in a measured magnetic field todetermine if a stride has been taken, and further provide a first userunderstandable signal if the angle that has been determined is withinthe known range of acceptable angles, and further provide a second userunderstandable signal if the angle that has been determined is outsideof the known range of acceptable angles on a first side of the range.10. The lower leg sensing device of claim 9 wherein module configured toprovide real-time data further comprises: first module wirelesslycoupled to the position angle sensor and the foot contact sensor; asignal member coupled to the first module, the signal member capable ofproviding a user understandable signal.
 11. The lower leg sensing deviceof claim 10 wherein the at least one user understandable signal compriseat least one of audible, visual and kinesthetic signals.
 12. The lowerleg sensing device of claim 11 wherein the first module furthercomprises a communication device and wherein the signal member comprisesat least one of the display of the communication device, a speaker ofthe communication device and a vibration mechanism of the communicationdevice.